Sacroiliitis (say-kroe-il-e-I-tis) is a painful condition that affects one or both sacroiliac joints. These joints sit where the lower spine and pelvis meet. Sacroiliitis can cause pain and stiffness in the buttocks or lower back, and the pain might go down one or both legs. Standing or sitting for a long time or climbing stairs can make the pain worse.

Sacroiliitis can be hard to diagnose. It can be mistaken for other causes of low back pain. It's been linked to a group of diseases that cause inflammatory arthritis of the spine. Treatment might involve physical therapy and medicines.


The pain of sacroiliitis most often occurs in the buttocks and lower back. It also can affect the legs, groin and even the feet. The pain can improve with movement. The following can make sacroiliitis pain worse:

  • Sleeping or sitting for a long time.
  • Standing a long time.
  • Having more weight on one leg than the other.
  • Stair climbing.
  • Running.
  • Taking large steps when moving forward.


Causes for sacroiliac joint issues include:

  • Injury. A sudden impact, such as a motor vehicle accident or a fall, can damage the sacroiliac joints.
  • Arthritis. Wear-and-tear arthritis, also known as osteoarthritis, can occur in sacroiliac joints. So can a type of arthritis that affects the spine, known as ankylosing spondylitis.
  • Pregnancy. The sacroiliac joints loosen and stretch for childbirth. The added weight and changed way of walking during pregnancy can stress these joints.
  • Infection. Rarely, a sacroiliac joint can become infected.


Sacroiliitis can cause difficulty with certain actions, such as bending, lifting, staying in one position and rising from being seated. The ongoing pain of sacroiliitis can lead to depression and loss of sleep.